Olympus i-SPEED 2, Инструкция по эксплуатации

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Understanding ispeed
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i
--SPEED LT,
i
--SPEED 2
Under some circumstances, it is desirable to record for a longer
time than the memory permits. It will be noted however, that some
high speed events are primarily horizontal or vertical in nature and
so it is sometimes found that the edges of the screen contain no
useful video information. This fact is used by the economy modes,
which reduce the active area of the sensor below the size
suggested by the frame speed. This reduced image size increases
the number of images which may be stored in the memory and
thereby the record time is increased.
Several economy modes are available. Wide modes remove the
top and bottom edges of the image, tall modes remove the left and
right edges and square modes remove the top, bottom, left and
right edges of the image. In square mode, the internal zoom
engine is again used to compensate for the reduced image size.
There is a further trade--off associated with frame speed and this is
discussed below.
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Shutter, Speed, Sensitivity
The sensor operates by capturing light, converting it to an
electronic facsimile of the optical image and supplying the memory
with the image while the cycle begins to repeat. The period during
which light is captured is called the “integration time”, “exposure
time” or “shutter time”. The shutter time is normally equal to the
maximum time available during the frame, called the “frame period”.
If the scene contains a very fast moving object, the object may
move an appreciable distance during the frame period and this will
cause the object to appear blurred. This “motion blur” is sometimes
undesirable, so the Olympus
i
-- SPEED LT,
i
-- SPEED 2 is able to
reduce the shutter time to a fraction of the frame period and this
causes the object to be “frozen” in each frame. The shutter time is
usually measured as the ratio between frame period and shutter
time, e.g. 10x means that the shutter is open for 1/10 of the frame
period.
Reducing the shutter time however, reduces the amount of time the
camera spends gathering light and the image will become dimmer.
For this reason, increasing the shutter setting will normally require
the addition of extra light to the scene.
A similar effect is found when the frame speed is increased. The
available shutter time is reduced because the frame period is
reduced -- the faster the frames are taken, the less time is spent on
each one. As a result of this, increasing frame speed will normally
require the addition of extra light to the scene.